1. Field of the Invention
The present invention relates to a method of producing a lead zirconate titanate-based thin film having excellent dielectric characteristics, a dielectric device including the same and a dielectric thin film.
2. Related Background Art
Of ferroelectric materials, lead-based ferroelectric materials such as PZT and PLZT are most practically used, because of their large residual dielectric polarization. Ferroelectric materials having been practically used, such as PZT and PLZT, are materials of sintered bulk, that is, multi-crystals whose orientations have not been controlled. In sintered bulk PZT, its characteristics such as permittivity and electric-mechanical bond coefficient are known to reach a maximum at morphotoropic phase boundary (MPB) in the vicinity of Zr/(Zr+Ti)=0.52.
Ferroelectric thin films of, for example, PZT and PLZT have a good chance of being used in many applications, such as ferroelectric memory and actuator. As to the ferroelectric thin films which are considered most promising in terms of the technique for controlling crystal orientation, crystal orientations of (100)/(001) have been used because of ease of film-forming and film-synthesizing, and there have been performed almost no film-syntheses nor film-characteristic evaluation adopting other crystal orientations; accordingly, it has not been clarified that excellent characteristics are shown by which orientation.
There have been examined ferroelectric thin films, such as PZT and PLZT, which have been formed by sputtering and sol-gel processing (Japanese Patent Application Laid-Open No. 2003-17767, Japanese Patent Application Laid-Open No. 6-350154); however, the inventors of this invention have been examining the formation of ferroelectric films, such as PZT and PLZT, by metal organic chemical vapor deposition (MOCVD) (Japanese Patent Application Laid-Open No. 2001-220676).
In sintered bulk PZT, as to its optimal composition, the characteristics such as permittivity and electric-mechanical bond coefficient are known to reach a maximum at morphotoropic phase boundary (MPB) in the vicinity of Zr/(Zr+Ti)=0.52; however, there have also been reported different values of the optimal composition of morphotoropic phase boundary, for example, Zr/(Zr+Ti)=0.80, and moreover, the composition has not been shown yet which have the most excellent characteristics.
Accordingly, in PZT thin films, it is not clarified yet with what orientation and composition they show the most excellent characteristics.
Ferromagnetic thin films of, for example, PZT having been reported up until now are mostly one-axis orientation films, but not epitaxial crystal thin films.